The structures of the filamentous bacteriophages Pf1 and fd will be studied using coordinated neutron and x-ray fiber diffraction and solid-state NMR spectroscopy. Neutron diffraction from specifically deuterated phage particles has been used to determine the positions of the five valine residues in Pf1 in three dimensions. Using this technique, the positions of additional residues in both virions will be determined. This will provide a detailed picture of the coat protein chain folding in the virions. Parallel 2H-NMR studies of specifically deuterated phage will also be used to characterize the structure and dynamics of the phage particles. A major strength of the proposed research is that the neutron diffraction and 2H-NMR experiments will utilize the same specimens. A method will be developed for combining structural information derived from solid-state NMR experiments with data from fiber diffraction studies. The approach to be taken will use restrained least-squares refinement of molecular models for the coat proteins to construct models of the virion structures consistent with orientational information derived from solid-state NMR, positional information derived from neutron diffraction from specifically deuterated specimens and high resolution x-ray fiber diffraction data. This unique coordination of different kinds of structural information will result in high resolution models for the structures of both PF1 and fd. The development of this coordinated approach to the study of macromolecular assemblies holds great promise for the study of the molecular architecture of many subcellular organelles.